What is the impact of obesity on cardio-vascular disease? – Part 4

Impact of obesity on cardio-vascular disease

• The higher prevalence of cardiovascular disease in obese individuals is indirectly mediated, to a large extent.
• This is by the increased frequency of various well known risk factors like hypertension, diabetes, and dyslipidemia.
• This could be either individually or as part of the metabolic syndrome.
• There are several ways in which obesity directly affects the cardiovascular system.
• Obesity also poses considerable challenges to making a precise cardiovascular diagnosis.
• This is because of limitations in physical examination as well as with various investigations.

Hypertension

• Among men, the prevalence of hypertension is 15% in those with BMI <25 and 42% if BMI is >30.
• In women, these are 15% and 38%, respectively.
• Blood pressure is the product of cardiac output and systemic vascular resistance.
• Cardiac output is increased in obese patients because of increased blood flow to the adipose tissue.
• We should expect the systemic vascular resistance to be low in obese individuals.
• This is because of the increased cross-sectional area of the vascular bed.
• It is often inappropriately normal or even high.
• This increases the likelihood of hypertension.

With increasing severity of obesity, hypertension becomes more prevalent.
• It may initially be diurnal, especially if there is coexisting sleep apnea.
• On the right side also there is an increase in the filling pressures, systolic pressure, and pulmonary vascular resistance.
• Increased pulmonary vascular resistance may be because of a combination of intrinsic pulmonary disease, sleep apnea/hypoventilation, recurrent pulmonary thromboembolism, or left ventricular dysfunction.
• All of these are more common in obese individuals.
• Pulmonary artery pressure is elevated in more than 50% of obese patients.
• It usually is only to a mild degree.
• Fifteen percent to 20% of patients with obstructive sleep apnea have pulmonary hypertension.
• This is often mild and ranges from 30 to 35 mm Hg.
• It is rare in the absence of daytime hypoxia.
• EKG signs of right ventricular overload are very late manifestations.

Conditions below are more common in those with obstructive sleep apnea.
• Nocturnal dysrhythmias.
• Right and left heart failure.
• Myocardial infarction.
• Stroke.
• Mortality.

Heart Stroke

• Increased BMI and waist–hip ratio are independent risk factors for stroke.
• This is even after adjusting for hypertension, hypercholesterolemia, and diabetes.
• Studies made by Physician’s Health study cohort of 21,414 men, those patients with BMI between 25 and 30 (8,105 men) and >30 (1,184 men) had a multiple adjusted relative risk of total stroke of 1.32 (95% CI, 1.14–1.54) and 1.91 (95% CI, 1.45–2.52), respectively when compared with men with BMI <25.
• In these groups the relative risk of ischemic stroke was 1.35 (95% CI, 1.15–1.59) and 1.87 (95% CI, 1.38–2.54) and hemorrhagic stroke was 1.25 (95% CI, 0.84–1.88) and 1.92 (95% CI, 0.94–3.93), respectively.
• With each 1-unit increase in BMI score, the multiple adjusted rate of ischemic stroke increased by 4% and 6% for hemorrhagic stroke.
• The underlying mechanisms by which increased BMI score affects stroke risk is independent of established risk factors such as hypertension and diabetes.
• This is not fully understood.
• This could be mediated by the prothrombotic and proinflammatory state (increased levels of C-reactive protein and lymphokines) in obesity.